Presentation Transcript

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When water in a river channel overflows the banks. Sudden heavy rainfall Industry Impermeable soil or bedrock Snowmelt Insufficient vegetation cover Long periods of rainfall Deforestation Intensive drainage systems Dams Impermeable road surfaces What is a flood? Why do
floods occur?

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Sudden heavy rainfall – More likely to occur in summer months when water is evaporated from soils leaving them hard and impermeable. Water is unable to infiltrate into the ground, river levels rise causing a flood.
Long periods of rainfall – Soils become saturated over time, excess water flows as overland flow into rivers, river levels rise causing a flood.
Snowmelt – Snow falls in winter and ground is frozen. In the spring snow begins to melt but the water is unable to infiltrate the soil as it is still frozen and impermeable. Therefore water flows overland and into rivers.
Impermeable soil and bedrock – These leave water unable to infiltrate into the ground causing excess overland flow into the rivers which causes the river level to rise.
Insufficient vegetation cover – when there is less vegetation less water is absorbed by plants so more water is infiltrated into the soil. Soils become saturated quicker causing more overland flow and as a result higher river levels. Physical

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Road surfaces – Rapid urbanization causes more impermeable surfaces and decreases the amount of permeable ground, therefore when heavy rains come water is unable to infiltrate causing more overland flow and higher river levels.
Drains – These carry more water to rivers in a very short time making river levels rise rapidly.
Deforestation – Less vegetation means that less water is taken in by leaves and roots causing the ground to become saturated sooner leading to more overland flow and rivers fill up quickly.
Dams – Their main purpose is to control river levels, but sometimes when it rains heavily they are unable to cope and this may have devastating effects.
Industry – Some industries add huge amounts of water to rivers which causes very high levels and lead to flooding. Human

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What caused the Bangladesh flood? Bangladesh is a country in Asia.
 It is located at the mouth of two of the world’s longest rivers, the Ganges and the Brahmaputra.
 Bangladesh has floods every year – but they seem to be getting worse.
 The country relies on the heavy monsoon rains to flood the rice fields, but to much rain can destroy the crop as well as the homes of the farmers.
 In four monsoon months, Bangladesh can get as much rain as London gets in two years.

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The Himalayas and Bangladesh get heavy monsoon rain. The last few years have been wetter then usual. The number of people living in India and Nepal is increasing. Trees Ganges Brahmaputra Confluence Point  The Himalayas and Bangladesh get heavy monsoon rain. The last few years have been wetter than usual .  The number of people living in India and Nepal is increasing. Trees have been cleared to make way for farmland and housing. The loss of trees has increase the amount of rainwater reaching the rivers.  The huge rivers brings the water quickly towards Bangladesh.  The population of Bangladesh is increasing rapidly. More and more land is being covered in buildings.  Bangladesh is a low flat country. 80% of it is less than 6m above sea level.  On reaching Bangladesh the rivers easily overflow their banks. Large areas of land are quickly flooded. H I M A L A Y A S Bay of Bengal Bangladesh India Nepal Dhaka Tibet

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How does Bangladesh
cope with flooding? Bangladesh suffers more from flooding than any other country in the world.
The problem is made worse because of the extreme poverty of people who live there.
In 1989, after a particularly bad flood, several wealthy countries joined with Bangladesh to set up the Flood Action Plan.
Under the Plan, billions of dollars are being spent on schemes which it is hoped will reduce the risk and danger of flooding.

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The Flood Action Plan for Bangladesh  Build dams to control river flow and hold back the monsoon rain water in reservoirs. Stored water can be used for irrigation and to generate cheap electricity.  Build embankments and deepen river channels to stop the river overflowing . The embankments would be up to 7m high in urban areas.  Build 5000 flood shelters in areas most at risk. These would be cheap to construct and provide a place of safety for almost everyone. They would be well stocked with food.

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 Improve flood warning systems. These would give early warnings of floods. They would also give instructions to people as to what they should do.  Provide emergency help when the floods arrive. Embankments would be repaired, people taken to safety and food and medical care provided to those in need.  Give after-care once the flood ends. Food, drinking water, tents, medicines and money would be available. Help would be given to plant seeds for ext years crops. Also. . .

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 There is no easy solution to Bangladesh’s flooding problem.
 The enormous size of the flooding problem and the shortage of money make the task almost impossible.
 Even the Flood Action Plan has not been welcomed by everyone.
 Many people are worried that such a large scheme could actually make the problem worse.

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Surma News Weekly Dhaka
15 September 1998 Worst ever floods hit Bangladesh The heaviest rains in living memory have left a trail of destruction across Bangladesh. Estimates suggest that over 7 million homes have been destroyed and at least 25million people made homeless. The official death toll is 2,779 although many more are still missing.
More than 80% of the country is covered in water. In some places only the tops of trees and buildings can be seen. Railways and roads have been swept away and Dhaka airport is still under water. Delivering emergency food and medical care to those in need has been almost impossible.
Few places have any electricity and there is no safe drinking water. The threat of disease is increasing and hospitals are already full of people suffering from dysentery and diarrhoea. Many of these people will not survive. The countryside areas have been worst hit. One family, sheltering on the corrugated iron roof of their flooded home, had lost their two oldest children to the flood. Their mother was in tears.
“They were just washed away in the night and never seen again. We have lost our homes, lost our land and lost our cattle. Our crops have been ruined and we have no food or money. Without help we will starve. Please help us…”

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How can the risk of
flooding be reduced?  There are many different ways of controlling rivers and reducing the risk of flooding.
 These are called flood prevention screens because they try to stop floods happening.
 Many people now believe that complete river and flood control is impossible.
 They say that flooding should be allowed to happen as a natural event.
 Flood prevention schemes can, in the long term, save money.
 They also improve water quality and help to support wildlife.

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Global Warming... What will happen to Bangladesh if sea level rises……

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Bay of Bengal With a sea level rise of 7m this is what Bangladesh will look like:

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With a further sea level rise to 14m Bangladesh will probably no longer exist: Bay of Bengal